NOT EXACTLY
ROCKET SCIENCE
Chimpanzees
Murder For Land
Discoverymagazine.com
Between 1998 and
2009, John
Mitani witnessed
18 murders
firsthand, and
found
circumstantial
evidence for
three more. But
no police were
ever called, for
these killers
were all
chimpanzees,
from the Ngogo
community in
Uganda’s Kibale
National Park.
Chimpanzees are
highly
intelligent
animals, capable
of great acts of
empathy,
technological
sophistication,
culture and
cooperation. But
they can also be
murderers.
Groups of
chimps, mostly
male, will mount
lengthy
aggressive
campaigns
against
individuals from
other groups,
attacking them
en masse and
beating them to
death. Their
reasons for such
killings have
long been a
source of debate
among
zoologists, but
the aftermath of
the Ngogo
murders reveals
an important
clue. After the
chimps picked
off their
neighbours, they
eventually took
over their
territory. It
seems that
chimps kill for
land.
The vast
majority of
these murders
were carried out
by groups of
Ngogo males on
patrol. These
patrols are
stern,
single-file
affairs. Males
march along the
borders of their
territories,
scanning for
other chimps and
neither feeding
nor socialising.
They monitor the
northeastern
part of their
territory with
particular
fervour and
indeed, 13 of
their 21 kills
took place here.
Of these
victims, 4 were
adult males and
9 were
youngsters. That
may seem like a
small number,
but for chimps,
these are severe
losses. At the
hands of the
Ngogo attackers,
the northeastern
community was
experiencing
death rates that
were 23 to 75
times higher
than those
observed in
other groups of
chimps. They
were even higher
(by around 5 to
17 times) than
the death rates
due to violence
between groups
of human
hunter-gatherers.
It’s clear that
the Ngogo chimps
are skilled at
waging war
against their
neighbours and
the
exceptionally
large males in
their number
probably
contribute to
their aptitude
for violence.
And because of
their aggressive
tactics, they
have increased
the size of
their territory
by some 22%,
expanding into
the northeast
area that their
neighbours once
called home.
With murder came
new real estate
to colonise.
Mitani’s
observations
back up other
anecdotal
evidence from
other parts of
Africa. In Gombe
National Park,
the Kasekala
community of
chimps took over
the territory of
the neighbouring
Kahama clan
after a series
of fatal
attacks. But the
former community
actually
splintered off
from the latter
some time
previously.
Elsewhere in the
Mahale
Mountains, one
group of chimps
annexed the
territory of
another. All the
males in the
latter group
mysteriously
disappeared, but
no murders were
ever directly
witnessed.
In contrast,
Mitani found
clear and direct
evidence that
the Ngogo chimps
killed off their
rivals and
commandeered
their land.
These
observations
don’t rule out
the alternative
ideas that the
attacks were
motivated by a
desire for more
mates. After
all, more
acreage could
attract more
females into the
group or
improves the
chances of
existing
members. But
Mitani’s
observations do
rule out at
least one idea
behind chimp
aggression –
that it’s a side
effect of
humans. Some
zoologists had
suggested that
by providing
food to wild
chimps, we were
instigating
conflict between
them, but that’s
clearly not the
case in Ngogo.
Much of this
behaviour might
seem familiar,
for it has
poignant echoes
of human
warfare. After
all, we also
kill each other
over resource.
Richard Wrangham,
a primatologist
from Harvard
University, has
suggested that
understanding
the reasons
behind chimp
violence could
help us to
understand and
address “the
roots of
violence in our
own species”.
Even so, Mitani
is very careful
about drawing an
analogy between
chimp and human
aggression,
given the myriad
of reasons that
humans have for
waging war.
Chimp expert
Frans de Waal
appreciates his
caution. He
says, “There
have been claims
made in the past
that since
chimps wage war
and we do as
well it must be
a characteristic
that goes back 6
million years,
and that we have
always waged
war, and always
will.
“There are many
problems with
this idea, not
the least of
which is that
firm
archaeological
evidence for
human warfare
goes back only
about 10-15
thousand years.
And apart from
chimpanzees, we
have an equally
close relative,
the bonobo, that
is remarkably
peaceful. The
recent discovery
of Ardipithecus
also adds to the
picture, as the
suggestion has
been that Ardi
was relatively
peaceful too.
The present
study provides
us with a very
critical piece
of information
of what
chimpanzees may
gain from
attacking
neighbours. How
this connects
with human
warfare is a
different
story.” |
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